The present invention relates to a friction drive for printers having at least two friction rolls which are mounted for independent rotation on a common shaft.
U.S. Ser. No. 871,459, filed Jan. 18, 1978, (see also German printed patent application No. 27 03 345) discloses a friction advance for individual sheets, wherein particularly each roll is a hollow element containing an electromagnetic coupling structure for coupling the roll to the common shaft. Each roll contains also an electromagnetically operated brake. This way, the rolls can be driven and stopped independently from each other.
This friction drive principle for two or more of the rolls has been employed quite successfully. There is, however, a need for a simplified version, in particular for those cases in which only one or the other of two rolls are to be driven, but never both together.